Predicting Mother Nature is never an exact science. Weather forecasters can get it wrong, leaving people dressed for a rainy day high and dry. And the further out researchers try to predict things like air temperature orsea ice cover, the more uncertainty there is.

Predicting when the Arctic will besea ice free in the summer months has occupied researchers for years. Estimates under high greenhouse gas emissions range from the year 2011 to 2098.

The complexity of Earth's atmosphere and oceans, and our limited understanding of those processes, are the main drivers of that uncertainty, saidJiping Liu, a sea ice researcher at the University of Albany in New York.

Liurecently published a study that narrowed down the range, predicting an ice-free Arctic summer by 2054 to 2058, based on current climate models.

"We know the climate models are not perfect," he said. "[But] we have to rely on them to make predictions."

Unknowns

There are several unknowns in sea ice modeling, Liu explained. First, researchers don't know how the ice reacts to inputs of warm water from the Pacific and Atlantic Oceans. There is an increased flow of warmer water into the Arctic, but we don't know how much of it is transferred to sea ice, he said.

"The bottom of sea ice is very sensitive to temperature changes," even to changes as little as 0.1 to 0.2 degrees, Liu noted.

Current models may therefore be underestimating the decline of Arctic sea ice during the summers, Liu said. "[And in] this sense, maybe the Arctic will be ice-free earlier."

We also don't know how sunlight penetrates sea ice to reach the water below, he explained. Thicker ice prevents sunlight from reaching seawater, stopping it from warming. But thinner ice lets the light through. Current climate models do not describe this process accurately, said Liu.

Finally, it's hard to determine how much of the change in sea ice cover is due to natural variability and how much is due to external forcing such as global warming.

"From my stance, 50 to 70 percent of sea ice decline is probably due to the increase of greenhouse gases [in the atmosphere]," said Liu. But that's a large range of uncertainty that needs to be narrowed down further, he added.

Still Robust

Julienne Stroeve, a sea ice scientist at the National Snow and Ice Data Center, agrees that not all the models are perfect. But they still give us a good idea of how areas will change under various emissions scenarios, she said.

"They all say the Arctic will warm more than any other place," Stroeve added. But their estimates of ice loss are lower than what scientists have observed.

The models that Liu used in his study were global climate models, which operate at very coarse scales, she said. Finer details like the ocean circulation in the Beaufort Sea—which controls the motion of sea ice in the Beaufort region—aren't incorporated.